Method and apparatus for transmitting/receiving data on multiple carriers in mobile communication system

ABSTRACT

A data transmission method and an apparatus to communicate data on multiple carriers in the mobile communication system are provided. A random access method of a terminal in a mobile communication system including primary and secondary cells operating on multiple carriers according to the present invention includes communicating data after random access in the primary cell, receiving, when the random access is triggered in the secondary cell, information for use in the secondary cell random access from the primary cell, transmitting a preamble in the secondary cell based on the received information, monitoring the primary cell to receive a Random Access Response for the secondary cell, and applying, when the Random Access Response for the secondary cell is received, the information carried in the Random Access Response to the secondary cell in which the preamble has been transmitted.

CROSS-REFERENCE TO RELATED APPLICATION(S)

This application is a continuation application of a prior applicationSer. No. 15/425,400, filed on Feb. 6, 2017, which is a continuationapplication of a prior application Ser. No. 14/875,050, filed on Oct. 5,2015, which has issued as U.S. Pat. No. 9,603,168 on Mar. 21, 2017,which is a continuation application of a prior application Ser. No.13/759,359, filed on Feb. 5, 2013, which has issued as U.S. Pat. No.9,414,409 on Aug. 9, 2016 and was based on and claimed priority under 35U.S.C. § 119(e) of a U.S. Provisional application No. 61/595,646, filedon Feb. 6, 2012, in the U.S. Patent and Trademark Office, a U.S.Provisional application No. 61/600,179, filed on Feb. 17, 2012, in theU.S. Patent and Trademark Office, a U.S. Provisional application No.61/612,950, filed on Mar. 19, 2012, in the U.S. Patent and TrademarkOffice, a U.S. Provisional application No. 61/620,957, filed on Apr. 5,2012, in the U.S. Patent and Trademark Office, and under 35 U.S.C. §119(a) of a Korean patent application number 10-2013-0006771, filed onJan. 22, 2013, in the Korean Intellectual Property Office, thedisclosure of each of which is incorporated by reference herein in itsentirety.

BACKGROUND OF THE INVENTION 1. Field of the Invention

The present invention relates to a mobile communication system. Moreparticularly, the present invention relates to a method and apparatusfor transmitting/receiving data on multiple carriers in the mobilecommunication system.

2. Description of the Related Art

Mobile communication systems have developed to provide subscribers withmobile voice communication services. With the advance of technology,mobile communications have evolved to support high speed datacommunication services as well as the standard voice communicationservices.

Recently, as a next generation mobile communication system, a standardfor Long Term Evolution (LTE) is being discussed by the 3rd GenerationPartnership Project (3GPP). LTE is designed to provide a downlink speedof up to 100 Mbps.

More recent studies are focused on the LTE-Advanced (LTE-A) forimproving data rate with the adaptation of several new techniques.Carrier Aggregation is one of the most distinct features of LTE-A.Unlike the a communication system using single uplink and singledownlink carriers per User Equipment (UE), the carrier aggregationenables a UE to be scheduled on multiple carriers in both uplink anddownlink.

By taking notice that a cell is configured with one downlink carrier andone uplink carrier, the carrier aggregation may be understood as if theUE communicates data via multiple cells. With the use of carrieraggregation, the maximum data rate increases in proportion to the numberof aggregated carriers.

In the following description, if a UE receives data through a certaindownlink carrier or transmits data through a certain uplink carrier,data is transmitted or received through control and data channelsprovided in a cell corresponding to center frequencies and frequencybands of the downlink and uplink carriers.

In the following description, carrier aggregation may be expressed insuch a way that multiple serving cells are configured. The multipleserving cells include a Primary serving cell (PCell) and at least oneSecondary serving Cell (SCell).

As used herein, the terms used to describe the embodiments of thepresent invention have the meanings as they do in LTE and as describedin 3GPP TS36.331 and TS36.321.

The legacy technology-based UE performs random access only to the PCell.If the UE attempts random access only to the PCell, this may cause SCelluplink performance degradation of the UE. The UE is likely to failuplink transmission in the SCells particularly when the PCell and SCellshave different uplink transmission timings.

SUMMARY OF THE INVENTION

Aspects of the present invention are to address at least theabove-mentioned problems and/or disadvantages and to provide at leastthe advantages described below. Accordingly, an aspect of the presentinvention is to provide a data transmission/reception method andapparatus that is capable of allowing the UE to perform random access inSCell as well as PCell, resulting in uplink performance improvement ofSCell.

Another aspect of the present invention is to provide a datatransmission/reception method and apparatus that is capable of allowingthe UE to reuse the information acquired in the PCell random access fornewly defined SCell random access procedure, resulting in reduction ofUE's implementation complexity.

Another aspect of the present invention is to provide a datatransmission/reception method and apparatus that is capable of allowinga UE to measure and validate its own mobility even in Radio ResourceControl (RRC) connection release state and to notify the eNB of themobility information when the RRC connection is reestablished.

In accordance with an aspect of the present invention, a random accessmethod of a terminal in a mobile communication system including primaryand secondary cells operating on multiple carriers is provided. Themethod includes communicating data after random access in the primarycell, receiving, when the random access is triggered in the secondarycell, information for use in the secondary cell random access from theprimary cell, transmitting a preamble in the secondary cell based on thereceived information, monitoring the primary cell to receive a RandomAccess Response for the secondary cell, and applying, when the RandomAccess Response for the secondary cell is received, the informationcarried in the Random Access Response to the secondary cell in which thepreamble has been transmitted.

In accordance with another aspect of the present invention, a terminalperforming random access in a mobile communication system is provided.The terminal includes primary and secondary cells operating on multiplecarriers includes a transceiver which communicates control informationand data with at least one cell, and a controller which controlsperforming random access in the primary cell, receiving, when the randomaccess is triggered in the secondary cell, information for use in thesecondary cell random access from the primary cell, transmitting apreamble in the secondary cell based on the received information,monitoring the primary cell to receive a Random Access Response for thesecondary cell, and applying, when the Random Access Response for thesecondary cell is received, the information carried in the Random AccessResponse to the secondary cell in which the preamble has beentransmitted.

Other aspects, advantages, and salient features of the invention willbecome apparent to those skilled in the art from the following detaileddescription, which, taken in conjunction with the annexed drawings,discloses exemplary embodiments of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above and other aspects, features, and advantages of certainexemplary embodiments of the present invention will be more apparentfrom the following description taken in conjunction with theaccompanying drawings, in which:

FIG. 1 is a diagram illustrating an architecture of a Long TermEvolution (LTE) system according to an exemplary embodiment of thepresent invention;

FIG. 2 is a diagram illustrating a protocol stack of an LTE systemaccording to an exemplary embodiment of the present invention;

FIG. 3 is a diagram illustrating an exemplary situation of carrieraggregation in a mobile communication system according to an exemplaryembodiment of the present invention;

FIG. 4 is a signal flow diagram illustrating a random access procedureaccording to an exemplary embodiment of the present invention;

FIG. 5 is a signal flow diagram illustrating a random access procedurebetween a User Equipment (UE) and an evolved Node B (eNB) according toan exemplary embodiment of the present invention;

FIG. 6 is a flowchart illustrating a UE procedure of a transmissionmethod according to an exemplary embodiment of the present invention;

FIG. 7 is a flowchart illustrating the UE procedure of the transmissionmethod according to another exemplary embodiment of the presentinvention;

FIG. 8 is a signal flow diagram illustrating signal flows between a UEand the eNB according to another exemplary embodiment of the presentinvention;

FIG. 9 is a flowchart illustrating UE procedure in a method according toan exemplary embodiment of the present invention;

FIG. 10 is a block diagram illustrating a configuration of a UEaccording to an exemplary embodiment of the present invention; and

FIG. 11 is a block diagram illustrating a configuration of an eNBaccording to an exemplary embodiment of the present invention.

Throughout the drawings, it should be noted that like reference numbersare used to depict the same or similar elements, features, andstructures

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The following description with reference to the accompanying drawings isprovided to assist in a comprehensive understanding of exemplaryembodiments of the invention as defined by the claims and theirequivalents. It includes various specific details to assist in thatunderstanding, but these are to be regarded as merely exemplary.Accordingly, those of ordinary skill in the art will recognize thatvarious changes and modifications of the embodiments described hereincan be made without departing from the scope and spirit of theinvention. In addition, descriptions of well-known functions andconstructions may be omitted for clarity and conciseness.

The terms and words used in the following description and claims are notlimited to the bibliographical meanings, but are merely used by theinventor to enable a clear and consistent understanding of theinvention. Accordingly, it should be apparent to those skilled in theart that the following description of exemplary embodiments of thepresent invention is provided for illustration purposes only and not forthe purpose of limiting the invention as defined by the appended claimsand their equivalents.

It is to be understood that the singular forms “a,” “an,” and “the”include plural referents unless the context clearly dictates otherwise.Thus, for example, reference to “a component surface” includes referenceto one or more of such surfaces.

Exemplary embodiments of the present invention are described below withreference to the accompanying drawings.

FIG. 1 is a diagram illustrating the architecture of a Long TermEvolution (LTE) system according to an exemplary embodiment of thepresent invention.

Referring to FIG. 1, the radio access network of the LTE system includesevolved Node Bs (eNBs) 105, 110, 115, and 120; a Mobility ManagementEntity (MME) 125; and a Serving-Gateway (S-GW) 130. The User EquipmentUE) 135 connects to an external network via eNBs 105, 110, 115, and 120and the S-GW 130.

The eNBs 105, 110, 115, and 120 correspond to legacy node Bs ofUniversal Mobile Communications System (UMTS). The eNBs 105, 110, 115,and 120 allow the UE establish a radio link and are responsible forcomplicated functions as compared to the legacy node B.

In the LTE system, all the user traffic including real time servicessuch as Voice over Internet Protocol (VoIP) are provided through ashared channel. Accordingly, there is a need of a device located in theeNB to schedule data based on the state information such as UE bufferconditions, power headroom state, and channel state. In order to meet adata rate of up to 100 Mbps, the LTE system adopts Orthogonal FrequencyDivision Multiplexing (OFDM) as a radio access technology.

The LTE system also adopts Adaptive Modulation and Coding (AMC) todetermine the modulation scheme and channel coding rate in adaptation tothe channel condition of the UE. The AMC is a technique for determiningthe modulation scheme and channel coding rate for the channel condition.

The S-GW 130 is an entity to provide data bearers so as to establish andrelease data bearers under the control of the MME 125. The MME 125 isresponsible for various control functions and connected to a pluralityof eNBs 105, 110, 115, and 120.

FIG. 2 is a diagram illustrating a protocol stack of the LTE systemaccording to an exemplary embodiment of the present invention.

Referring to FIG. 2, the protocol stack of the LTE system includesPacket Data Convergence Protocol (PDCP) 205 and 240, Radio Link Control(RLC) 210 and 235, Medium Access Control (MAC) 215 and 230, and Physical(PHY) 220 and 225.

The PDCP 205 and 240 is responsible for IP headercompression/decompression. The RLC 210 and 235 is responsible forsegmenting the PDCP Protocol Data Unit (PDU) into segments in anappropriate size for Automatic Repeat Request (ARQ) operation.

The MAC 215 and 230 is responsible for establishing connection to aplurality of RLC entities so as to multiplex the RLC PDUs into MAC PDUsand demultiplex the MAC PDUs into RLC PDUs. The MAC PDUs are deliveredto the PHY 220 and 225. The MAC 215 and 230 demultiplexes the MAC PDUsfrom the PHY 220 and 225 into RLC PDUs and delivers the RLC PDUs tocorresponding RLC entities.

The PHY 220 and 225 performs channel coding on the MAC PDU and modulatesthe MAC PDU into OFDM symbols to transmit over radio channel or performsdemodulating and channel-decoding on the received OFDM symbols anddelivers the decoded data to the higher layer.

FIG. 3 is a diagram illustrating an exemplary situation of carrieraggregation in the mobile communication system according to an exemplaryembodiment of the present invention.

Referring to FIG. 3, typically an eNB is capable of transmitting andreceiving signals to and from the UE 330 on multiple carriers acrossdifferent frequency bands. For example, the eNB 305 may be configured touse the carrier 315 with center frequency f1 and the carrier 3210 withcenter frequency f3. If carrier aggregation is not supported, the UE 330has to transmit/receive data unit one of the carriers 310 and 315.However, the UE 330 capable of carrier aggregation can transmit/receivedata using both of the carriers 310 and 315.

The eNB 305 is capable of increasing the amount of the resource to beallocated to the UE 330 capable of carrier aggregation according to thechannel condition of the UE 330 to increase the data rate.

Unlike the example shown in FIG. 3, the eNB may be configured withRemote Radio Heads (RRHs) that are distributed to transmit and receivesignals at a location geographically far from the eNB. The uplinktimings of the serving cell may be set to center around the eNB and thecells defined by the RRHs.

If the UE is configured with SCell having a coverage area different fromthat of the PCell and thus required to set a different uplinktransmission timing, it is necessary for the UE to perform random accessprocedure in the corresponding SCell for determining the uplinktransmission timing of the SCell.

Exemplary embodiments of the present invention propose a method andapparatus for performing SCell random access to set a SCell uplinktransmission timing different from the PCell uplink transmission timingwhich has been set already.

FIG. 4 is a signal flow diagram illustrating a random access procedureaccording to an exemplary embodiment of the present invention.

Referring to FIG. 4, the random access procedure includes 4 steps oftransmitting a preamble, receiving a Random Access Response,transmitting message 3, and contentions resolution. The last two stepsmay be omitted depending on the case.

If a random access is triggered by a certain reason, the UE 405determines the preamble transmission timing, transmission resource(frequency and time resources), and preamble to be transmitted by takingnotice of the random access transmission resource information of thecell in which the random access is to be performed. The UE sends the eNB410 the preamble at the preamble transmission power calculated based onthe current channel condition, e.g. path loss, at step 415.

Upon receipt of the preamble transmitted by the UE, the eNB 410generates and sends a Random Access Response message to the UE 405 atstep 420. The Random Access Response message includes UE's uplinktransmission timing adjustment command (Timing Advance (TA)) or uplinktransmission resource information (Uplink (UL) grant) for message 3transmission.

Upon receipt of the Random Access Response message, the UE 405 sends theeNB 410 the message 3 at step 425. The message 3 includes UE identifiersuch that upon receipt of the message 3 the eNB send the UE a responsewhich is referred to as Contentions Resolution at step 430. If the eNB410 does not receive the preamble, the Random Access Response message isnot transmitted such that the UE 405 also does not receive the RandomAccess Response message. After a predetermined time has elapsed, the UE405 retransmits the preamble at a power increased as much aspredetermined amount as a part of uplink power control.

The random access procedure may be performed for various reasons. Forexample, the UE 405 may initiate the random access to request the eNB410 for scheduling or to establish or reestablish the RRC connection.The UE 405 is also capable of initiating the random access to the targetcell after handover.

In the aforementioned cases, it is preferred for the UE 405 to initiatethe random access in the PCell. In the case of attempting SCell uplinktransmission timing configuration as described above, however, therandom access should be initiated in the corresponding SCell.

According to an exemplary embodiment of the present invention, the eNBcontrols whether to initiate a SCell random access unlike the PCellrandom access. According to exemplary embodiments of the presentinvention, the UE is prevented from initiating SCell random accessvoluntarily in order to maintain the random access load of the SCell atan appropriate level and to initiate the UE's random access at a timingindicated by the eNB.

FIG. 5 is a signal flow diagram illustrating a random access procedurebetween a UE and an eNB according to an exemplary embodiment of thepresent invention.

Referring to FIG. 5, the UE 505 having no RRC connection selects thecell 1 510 according to predetermined criteria among plural connectablecells and acquires system information from the sell 1 at step 520. Thesystem information is broadcast in the control message referred to assystem information block (systeminformationblock) so as to be receivedby the UEs selected the corresponding cell. The system information block2 (systeminformationblock2) includes the following information necessaryfor the UE to perform random access in the corresponding cell. Therandom access-related information includes:

-   -   Maximum preamble transmission times (preambleTransMax): maximum        number of preamble transmission times allowed until the UE take        a predetermined action while perform random access. The        predetermined action can be RRC connection reestablishment        operation. The eNB sets preambleTransMax to an appropriate value        to prevent the preamble transmission from repeating infinitely.    -   Random Access Response window size (ra-ResponseWindowSize): The        random access response window (ra-window) is a time duration        monitoring the Physical Downlink Control Channel (PDCCH) in        order for the UE to receive a Random Access Response (RAR)        message. If the UE fails to receive a valid random access        response message until the Random Access Response window        expires, the UE is capable of retransmitting the preamble.    -   Random access transmission resource information: For example,        the information on the subframe allowing the UE to transmit the        preamble, information on the frequency resource, and information        about the preamble format.

The UE takes an action which is supposed to be taken in the case wherethe RRC connection has not been established in the cell 1, e.g.monitoring the paging channel and measuring neighbor cells.

In this state, if an RRC connection setup is triggered at a certaintiming (e.g. the UE receives a paging signal or data or control messageto be transmitted) is generated at step 525, the UE establishes an RRCconnection with the cell 1 at step 530.

The eNB allocates Signaling Radio Bearer (SRB) for exchanging RRCcontrol message between the UE and the eNB and Data Radio Bearer (DRB)for exchanging user data between the UE and the eNB to communicatedownlink and uplink data with the UE using the radio bearers.

If the random access is triggered by a certain reason at a certaintiming at step 535, e.g. if the eNB instructs the UE to initiate randomaccess or if the UE needs to request the eNB for transmission resource,the UE determines the preamble for transmitting the preamble based onthe random access-related information acquired from the systeminformation block 2 (systeminformationblock2) and transmits the preambleat step 540.

For example, if the UE transmits the preamble at uplink subframe n, theRandom Access Response window starts at downlink subframe n+m. The UEmonitors to receiving a Random Access Response message for the RandomAccess Response window. m is a value defined in the standard and set tobe 2 or 3.

The UE monitors PDCCH to detect the scheduling of an identifier mappedto the transmission resource with which the preamble has beentransmitted, determines whether the received random access responseincludes the identifier mapped to the preamble in the header, and if sosaves the uplink transmission resource allocation information (ULgrant), Transmission Power Control (TPC), and uplink transmission timeadjustment information (Timing Advance or TA) contained in the validrandom access response message at step 545.

If no valid Random Access Response message (RAR) is received until theRandom Access Response window expires, the UE retransmits the preamble.The number of preamble retransmission times is limited by thepreambleTransMax included in the system information block 2, and if therandom access fails even with the preambleTransMax preambletransmissions, the UE determines that a significant problem has occurredand initiates RRC connection reestablishment procedure.

The UE applies at least one of the uplink transmission resourceallocation information (UL grant), Transmission Power Control (TPC), anduplink transmission time adjustment information (Timing Advance or TA)carried in the valid random access response message to uplinktransmission in the first serving cell at step 550.

The UE adjusts the transmission start timing of the uplink subframe n ofthe first serving cell to precede the start timing (start boundary) ofthe downlink subframe n of the first serving cell as much as TA,increases or decreases the uplink transmission power as much as theamount indicated by TPC, and selects uplink transmission resource of thefirst serving cell.

The UE performs uplink transmission at step 555. The UE selects theserving cell in which the RAR has been received as the first servingcell.

If carrier aggregation is not configured for the UE, if carrieraggregation is configured but only one serving cell has uplink, or ifcarrier aggregation is configured with plural serving cells but only oneserving cell is allowed for random access, there is no need for acriteria to determine the cell to which the information carried in theRAR is applied. According to an exemplary embodiment of the presentinvention, the cell in which the RAR has been received is selected asthe serving cell to which the information carried in the RAR is applied.

The UE performs Physical Uplink Shared Channel (PUSCH) transmission inthe cell 1 by applying the UL grant of the RAR at step 555. Typically,the synchronous Hybrid Automatic Repeat Request (HARQ) process isapplied to the PUSCH transmission. In the synchronous HARQ transmission,if a HARQ NACK is received, the sender performs retransmission using thesame transmission resource as the previous transmission.

In this case, the UE is capable of performing HARQ transmission maximumretransmission times of maxHARQ-Tx and, if the HARQ transmission failstill then, stops transmission of the PUSCH. The maxHARQ-Tx is the valuefor preventing the PUSCH transmission of one MAC PDU from repeatinginfinitely and preferably set per UE according to whether the UE channelstatus considered by the eNB scheduler and delay sensitivity of theservice configured for the UE.

The UE is provided with the following three types of maxHARQ-Txparameters:

-   -   First maxHARQ-Tx: parameter the UE acquires through        systeminformationblock2 of the serving cell    -   Second maxHARQ-Tx: parameter the UE acquires through dedicated        RRC control message such as RRC connection setup message        (RRCConnectionSetup) in the RRC connection setup procedure in        PCell    -   Third maxHARQ-Tx: parameter the UE acquires through dedicated        RRC control message such as RRC Connection Reconfiguration        message (RRCConnectionReconfiguration) in the procedure of        adding SCell configured with uplink

If the preamble transmitted at step 540 is the dedicated preamble, theUE performs PUSCH transmission by applying the second maxHARQ-Tx at step555. If the preamble transmitted at step 540 is a random preambleselected by the UE, the UE performs PUSCH transmission by applying thefirst maxHARQ-Tx. If the dedicated preamble is applied, then the eNBknows the UE at the PUSCH transmission timing; and if the randompreamble is applied, then the eNB does not know the UE at the PUSCHtransmission timing.

Although described below, the UE applies the third maxHARQ-Tx to thePUSCH transmission using the UL grant acquired in the SCell randomaccess procedure.

The UE performs downlink data reception and uplink data transmissionaccording to the above described principle in the cell 1.

If the data amount for the UE increases, the eNB controlling the cell 1is capable of determining increase of the data rate by adding SCell tothe UE. The eNB controlling the cell 1 determines to add a SCell for theUE at step 560.

In this case, if the location of the transmission/reception device ofthe SCell to be newly added differs from that of the PCell, e.g. if thePCell is a macro cell and the SCell is of an RRH, the eNB provides theUE with SCell configuration information and the information necessaryfor performing random access in the S Cell at step 565.

According to an exemplary embodiment of the present invention, the eNBprovides the UE with a part rather than whole of the SCell randomaccess-related information so as to reuse the information used in thePCell. For example, the UE receives the maximum preamble transmissiontimes (preambleTransMax) and random access transmission resourceinformations for use in the SCell but reuses the random access responsewindow size (ra-ResponseWindowSize) used in the PCell. This is becausethe preambleTransMax and the random access transmission resourceinformation are parameters for controlling preamble transmission thatare preferred to be set to the values dedicated to the correspondingserving cell. ra-ResponseWindowSize is the parameter related to theserving cell for receiving RAR rather than the serving cell transmittedthe preamble and thus it is preferred to reuse the value defined for usein the PCell.

The UE receives a PDCCH order instructing to initiate random accessprocedure at step 570. The PDCCH order is a command instructing a UE toinitiate random access in a certain cell and is specified in TS36.211.The PDCCH order is transmitted/received in Downlink Control Information(DCI) format 1A, and CRC is scrambled with C-RNTI of the correspondingUE. Each field is coded as shown in Table 1.

TABLE 1 PDCCH field Size (bit) Value Flag for format0/ 1 1 format1Adifferentiation Localized/Distributed 1 0 VRB assignment flag RBassignment 5~13 all 1 Preamble index 6 Index of preamble to be used byUE in random access procedure PRACH mask index 4 PRACH mask index to beapplied in random access procedure remaining 3 or 4 all 0

If the PDCCH order is received at subframe [n], the UE transmits thepreamble at subframe [n+x1] in cell 2 with the application of thepreamble index at step 575. Here, x1 is an integer greater than x andcorresponds to the first valid Physical Random Access Channel (PRACH)occasion since [n+x]. x is the time necessary to take an action fortransmitting the preamble and defined as a relatively great value inconsideration of the low-end UE lack in processing capability. In thecurrent standard, this value is defined to be set to 6. The valid PRACHoccasions denotes the PRACH occasions allowed for UE's preambletransmission among the PRACH occasions defined by the PRACHconfiguration information and are indicated by the PRACH mask index.Since the PRACH mask index is specified in TS36.321 and TS36.213, adetailed description thereof is omitted.

After transmitting the random access preamble in the SCell, the UEmonitors PDCCH of the PCell to determine whether RAR is received in thera-Window. The window size is set to the random access response window(ra-ResponseWindowSize) acquired for use in PCell at step 520.

Typically, if a preamble is transmitted in a SCell, it is much intuitiveto receive the RAR in the SCell. The RAR is addressed with a specificidentifier, i.e. RA-RNTI, unlike user data. In this case, the UE shouldmonitor to detect RA-RNTI as well as C-RNTI to receive RAR in the SCellin the SCell, and this increases the UE complexity. However, if the RARreception is restricted to the PCell, what is to be monitored by the UEin the S Cell is only the C-RNTI such that it is possible to avoid theincrease of the UE complexity.

The UE according to an exemplary embodiment of the present invention ischaracterized in that although a preamble has been transmitted in aSCell the UE monitors the PDCCH of the PCell to receive the RAR withRA-RNTI during the ra-Window defined by the random access responsewindow size (ra-ResponseWindowSize) for use in the PCell.

If no valid RAR is received, the UE retransmits the preamble in theSCell. If the random access procedure fails even with the predeterminednumber of preamble transmissions, the UE stops preamble transmission toavoid more uplink transmission in the SCell.

The UE transmits a random access preamble in a SCell and then monitorsthe PCell to receive an RAR in response to the preamble. If RAR is notreceived, the UE retransmits the random access preamble in the SCell.

If a valid RAR is received in the PCell at step 580, the UE applies theUL grant, TPC, and TA carried in the valid RAR to the uplinktransmission in the second serving cell at step 585. In this case, thesecond serving cell is the serving cell in which the UE has transmittedthe preamble other than the serving cell in which the RAR has beenreceived.

The UE adjusts the transmission start timing of the uplink subframe n ofthe second serving cell to precede the start time (start boundary) ofthe downlink subframe n of the second serving cell as much as TA andincreases or decreases the uplink transmission power of the secondserving cell as much as an amount indicated by the TPC. The RAR includes3-bit TPC as shown in Table 2.

TABLE 2 TPC Command Value (in dB) 0 −6 1 −4 2 −2 3 0 4 2 5 4 6 6 7 8

Typically, the TPC relates to the PUSCH transmission power control ofthe service cell in which the RAR is received. In the case that the UEcapable of performing random access in multiple serving cells hastransmitted a preamble in a sell, however, the TPC relates to the PUSCHtransmission control of the second serving cell, i.e. the serving cellin which the preamble has been transmitter, other than the serving cellin which the RAR has been received.

The UE selects the transmission resource of the second serving cell foruplink transmission. The UE performs uplink transmission at step 590. Asdescribed above, if carrier aggregation is not configured for the UE, ifcarrier aggregation is configured but only one serving cell has uplink,or if carrier aggregation is configured with plural serving cells butonly the PCell is allowed for random access, there is no need for acriteria to determine the cell to which the information carried in theRAR is applied. According to an exemplary embodiment of the presentinvention, the cell in which the RAR has been received is selected asthe serving cell to which the information carried in the RAR is applied.

However, if the UE has transmitted a preamble in a SCell or if the UE iscapable of performing random access in an SCell as well as a PCell, theaim of the random access procedure may not be accomplished. Unlike thecase in which the UE having only one serving cell allowing for randomaccess operates with the information carried in the RAR received in theserving cell without problem, the UE having multiple serving cellallowing for random access applies the information carried in the RARreceived in the serving cell in which the preamble has been transmittedother than the serving cell in which the RAR has been received. Thismeans that if the UE having multiple cells allowing for random accessreceives the RAR in response to a preamble transmitted in a SCell, theUE applies the TA, TPC, and UL grant carried in the RAR to the servingcell in which the preamble has been transmitted other than the servingcell in which the RAR has been received.

The UE performs Physical Uplink Shared Channel (PUSCH) transmission incell to by applying the UL grant of the RAR at step 590. At this time,the UE controls the PUSCH transmission by applying the third maxHARQ-Txacquired at step 565.

FIG. 6 is a flowchart illustrating the UE procedure of the transmissionmethod according to an exemplary embodiment of the present invention.

Referring to FIG. 6, the UE acquires random access-related informationat step 605. The random access-related information may include Randomaccess transmission resource information of PCell (prach-ConfigIndex,etc.), random access transmission resource information of SCell(prach-ConfigIndex, etc.), ra-ResponseWindowSize, preambleTransMax1,preambleTransMax2, maxHARQ-Tx 1, maxHARQ-Tx 2, and maxHARQ-Tx 3.

This information is acquired through various control message such assystem information block and dedicated control message transmitted atdifferent timings. For example, the PCell random access transmissionresource information, ra-ResponseWindowSize, and preambleTransMax1 maybe acquired through systeminformationblock2 of PCell, and maxHARQ-Tx 2may be acquired through RRC Connection Setup message. ThepreambleTransMax2, maxHARQ-Tx 3 may be acquired through the RRCConnection Reconfiguration message for adding SCell.

A random access procedure is triggered at step 610. For example, therandom access procedure may be triggered when data having a highpriority occurs in the UE, when the eNB commands the UE to performrandom access, or when the UE needs to reestablish RRC connection.

The UE determines the earliest valid PRACH occasion in the near futureusing the random access transmission resource information and transmitsthe preamble at the PRACH occasion at step 615. The preambletransmission power is configured in consideration of downlink path lossof the serving cell in which the preamble is transmitted.

The UE monitors the PDCCH of PCell to receive RAR in response to thepreamble for a predetermined time duration at step 620. The timeduration is ra-Window. If the preamble has been transmitted in thePCell, the maximum size of ra-Window is determined by applyingra-ResponseWindowSize acquired from the system information of thecorresponding serving cell. If the preamble has been transmitted inSCell, the maximum size of ra-window is determined by applying thera-ResponseWindowSize acquired in the system information of otherserving cell (e.g. PCell) than the corresponding serving cell (i.e.SCell).

If a valid RAR is received during the ra-Window, the procedure goes tostep 630. Otherwise, if a valid RAR is not received, the procedure goesto step 625. If a valid RAR has been received, then the UE has decodedthe scheduling information with the RA-RNTI mapped to the transmissionresource on which the UE has transmitted the preamble through the PDCCHof the PCell for the time duration of ra-Window and the ID of the RAR(RAPID) received according to the scheduling information matches thepreamble transmitted by the UE.

If a valid RAR is not received during the ra-Window, the UE determineswhether preamble retransmission is possible and, if so, retransmits thepreamble at step 625, and returns the procedure to step 620. In the caseof PCell, the preamble can be retransmitted until the number of preambletransmission times reaches preambleTransMax 1. In the case of SCell, thepreamble can be retransmitted until the number of preamble transmissiontimes reaches preambleTransMax2.

The UE determines whether the cell in which the preamble has beentransmitted is PCell or SCell at step 630. If the preamble has beentransmitted in PCell, the procedure goes to step 635 and, otherwise, tostep 650.

If the preamble has been transmitted in PCell, the UE applies TA to theserving cell in which RAR has been received at step 635. For example,the UE adjusts the uplink subframe boundary of the serving cell in whichthe RAR has been received to precede the downlink subframe boundary ofthe serving cell in which the RAR has been received as much as TA.

The UE sets the uplink transmission power of the serving cell using theTPC carried in the RAR at step 640. The UE calculates the PUSCHtransmission power of the serving cell by summing the transmission poweradjustment values indicated by the TPC.

The UE transmits the PUSCH in uplink of the serving cell, in which theRAR has been received, by applying uplink resource allocationinformation (UL grant) carried in the RAR at step 645. If the preambletransmitted at step 615 is dedicated preamble, the PUSCH is transmittedwith the application of maxHARQ-Tx 2 and, otherwise if the preamble israndom preamble, the PUSCH is transmitted with the application ofmaxHARQ-Tx 1.

If the preamble has been transmitted in SCell, the UE applies the TA tothe serving cell in which the preamble has been transmitted other thanthe serving cell in which the RAR has been received at step 650. The UEmoves up the uplink subframe boundary of the serving cell in which thepreamble has been transmitted as much as TA as compared to the downlinksubframe boundary of the serving cell in which the preamble has beentransmitted. The uplink transmission timing is applied to the uplinktransmission in all serving cells belonging to the same TA Group (TAG)as the serving cell in which the preamble has been transmitted.

The TAG is the group of at least one serving cell having the same uplinktransmission timing. If the serving cells belonging to a TAG share thesame uplink transmission timing, then the uplink transmission timings ofthe serving cells are identical with each other and the serving cellsestablishes or loses the uplink synchronization simultaneously.Furthermore, the uplink transmission timings are adjustedsimultaneously.

TAG can be categorized into one of primary TAG and secondary TAG. Theprimary TAG is the TAG including the PCell, and the secondary TAG is theTAG including only SCells. The random access is permitted only in thePCell for the primary TAG and only in a predetermined SCell for thesecondary TAG. If a SCell is added, the eNB notifies the UE whether theS Cell belongs to the primary TAG or a secondary TAG and, if the SCellbelongs to the secondary TAG, which secondary TAG the SCell belongs to.

The UE sets the uplink transmission power of the serving cell in whichthe preamble has been transmitted at step 615 using the TCP carried inthe RAR at step 655. The UE calculates the PUSCH transmission power ofthe serving cell by summing the transmission power adjustment valuesindicated by TPC.

The UE transmits the PUSCH in uplink of the serving cell, in which thepreamble has been transmitted, by applying the UL grant carried in theRAR in step 660. The PUSCH is transmitted with the application ofmaxHARQ-Tx 3.

FIG. 7 is a flowchart illustrating a UE procedure of a transmissionmethod according to another exemplary embodiment of the presentinvention. Since steps 705, 710, 715, 720, and 725 of FIG. 7 areidentical with steps 605, 610, 615, 620, and 625 of FIG. 6, detaileddescriptions thereon are omitted herein.

Referring to FIG. 7, once a valid RAR has been received at step 720, theUE determines whether it is configured to perform the random access onlyin the PCell or both the PCell and S Cell at step 730. If the UE isconfigured to perform the random access only in the PCell, the proceduregoes to step 735 and, if the UE is configured to perform the randomaccess in both the PCell and SCell, to step 750.

Since steps 735, 740, 745, 750, and 755 of FIG. 7 are identical withsteps 635, 640, 645, 650, and 655 of FIG. 6, detailed descriptionsthereon are omitted herein.

After applying the TPC at step 755, the UE transmits the PUSCH, inuplink of the serving cell in which the preamble has been transmitted,by applying the UL grant carried in the RAR at step 760. If the servingcell in which the preamble has been transmitted at step 715 is the PCelland if the preamble is the dedicated preamble, the PUSCH is transmittedwith the application of maxHARQ-Tx 2 and, if the preamble is the randompreamble, with the application of maxHARQ-Tx 3.

With the commercialization of various packet services, small packets arefrequently generated sporadically. In the mobile communication systemsincluding LTE system, it is inevitable to establish a signalingconnection and data bearer in order to transmit a packet regardless ofhow small the packet is. In the above procedure, a large amount ofcontrol messages are exchanged.

If a connection to transmit/receive small amounts of data is establishedand released frequently, this is likely to cause overload in the networkand accelerate battery power consumption of UE.

One approach to address this issue is that the UE stays in the connectedstate. However, if the UE with high mobility stays in the connectedstate, the frequent handover generates large amount of control messagetraffic between UE and eNB, between eNBs, and between eNB and MobilityManagement Entity (MME) so as to lose the gain achieved by maintain theconnected state. As a result, staying in the connected state is astrategy useful only when the UE has no data to be transmitted and/orreceived.

Since the UE mobility is managed by the eNB once the UE enters theconnected state, the eNB estimates the velocity of the UE and determineswhether to apply the strategy of staying in connected state based on thevelocity of the UE. The velocity estimation may be performed after apredetermined duration elapses since the UE has entered the connectedstate. However, it may become necessary to determine whether to releaseor maintain the connection before starting velocity estimation.Furthermore, since the eNB may trigger DRX configuration according tothe velocity of the UE, it is preferred for the UE to notify the eNB ofthe UE's velocity as soon as possible.

Another exemplary embodiment of the present invention proposes a methodand apparatus for measuring and/or validating the mobility of the UEcontinuously in the state where the RRC connection with the eNB isreleased and, when the RRC connection is established, notifying the eNBof the RRC connection establishment.

FIG. 8 is a signal flow diagram illustrating signal flows between the UEand the eNB according to another exemplary embodiment of the presentinvention.

Referring to FIG. 8, if the system information block 3(systeminformationblock3) is received in the current serving cell, e.g.cell 1 810 at step 815, the UE 805 in the state that the RRC connectionhas been released saves the parameters related to the mobility statethat are included in the memory. The mobility state-related parametersinclude t-Evaluation, n-CellChangeMedium, and n-CellChangeHigh. Thisinformation is used for determining whether the mobility state of the UEis High-mobility state, Medium-mobility state, or Normal-mobility state.

If the number of cell changes (or number of cell reselections) duringthe t-Evaluation is equal to or greater than n-CellChangeHigh, the UEdetermines that its mobility state is High-mobility state. If the numberof cell changes (or number of cell reselections) is less thann-CellChangeHigh and equal to or greater than n-CellChangeMedium, the UEdetermines that its state is Medium-mobility state. When these twoconditions are not fulfilled, the UE determines that its state isNormal-mobility state.

The UE adjusts the cell reselection-related parameters based on themobility state according to a predetermined rule. The method foradjusting the cell-reselection parameters is specified in TS36.304.

The UE determines its mobility state based on the above informationsand, if necessary, update the mobility state at step 820. If the UE hasthe information on the UE's real velocity acquired from a locationmeasurement system such as a Global Navigation Satellite System (GNSS),the UE is capable of the mobility state based on the real velocityinformation.

If a neighbor cell having the channel state better than that of thecurrent serving cell is found at a certain time and the channel state ismaintained over a predetermined duration, the UE performs cellreselection, i.e. reselects the neighbor cell 2 825 at step 830. If theold serving cell and the reselected serving cell operate on the samefrequency, this cell reselection is referred to as intra-frequency cellreselection.

The parameters related to mobility state may be configured according tothe network deployment. For example, the parameters may be configuredaccording to the size of the cell deployed in a predetermined area.Since the cell size is determined depending on the frequency, if the UEperforms intra-frequency cell reselection, the mobility state parametersare likely to be identical with those of the old serving cell.Accordingly, in the case of intra-frequency cell reselection, the UE iscapable of calculating and updating the mobility state before receivingthe system information block 3 (systeminformationblock3) in the newlyselected cell at step 835. The UE increments the number of cellreselections for t-Evaluation NCR by 1 and determines the mobility stateby applying the new NCR.

Afterward, the UE selects a new cell, e.g. cell 3 840, at step 845. Ifthe new serving cell operates on a frequency different from that of theold serving cell, this cell reselection is referred to asinter-frequency cell reselection. In the case of inter-frequency cellreselection, the mobility state parameters of the new operationfrequency is likely to differ from the mobility state parameters of theold operation frequency.

The UE receives the system information block 3 (systeminformationblock3)of the new cell at step 850 to update the mobility state parameters. TheUE determines the mobility state based on the newly updated mobilitystate parameters. Once the mobility state parameters are updated, the UEupdates t is mobility state as follows at step 855.

During the t-Evaluation arriving first after change of the mobilitystate parameters (i.e. before the mobility state in the new cell or onthe new frequency), the UE maintains the mobility state used in the oldserving cell (i.e. the most recent mobility state). The UE adjusts thecell reselection-related parameters by applying the mobility state onthe old frequency. That is, the UE uses the mobility state used in theold cell but the cell reselection parameters (e.g. q-HystSF) received inthe current cell. If the mobility state is determined based on the newmobility state parameters due to the elapse of the t-Evaluation, the UEadjusts the cell reselection parameters by applying the new mobilitystate.

If it becomes necessary to establish an RRC connection at a certain timeat step 860, the UE sends the eNB an RRC Connection Request message atstep 865 and receives an RRC Connection Setup message from the eNB atstep 870. The UE sends the eNB a RRC Connection Setup Complete messageincluding the mobility state at step 875. The UE may reports only themobility state or the mobility state, t-Evaluation, and NCR used indetermining the current mobility state. The UE may report theinformation on whether GNSS is operating currently and real velocity ofthe UE which has been measured with the assistance of the GNSS. Themobility state can be updated quickly and precisely with the assistantof the GNSS. The eNB is capable of configuring the UE to determine themobility state continuously with the assistance of GNSS and reports theresult when a predetermined condition is fulfilled. For example, the eNBsends a control message for configuring the mobility state report to theUE which has reported the assistance of GNSS at step 880. This controlmessage may include the information instructing to report the mobilitystate when the mobility state changes or when the velocity of the UEmaintains a level higher than a predetermined threshold value over apredetermined duration.

If the mobility state report condition is fulfilled at step 885, the UEgenerates an RRC control message to report the mobility state 2 to theeNB at step 890.

The eNB adjusts the DRX period to be applied to the UE (e.g. shortensthe DRX period when the UE velocity is higher than a predeterminedthreshold) or releases the RRC connection (e.g. releases the RRCconnection when it is predicted that handover occurs frequently if theRRC connection is maintained, based on the reported UE velocity).

FIG. 9 is a flowchart illustrating UE procedure in the method accordingto an exemplary embodiment of the present invention.

Referring to FIG. 9, the UE in idle state acquires the mobility stateparameters in the system information of the serving cell andmaintains/manages the mobility state at step 905. If the velocity of theUE is measured with the assistance of GNSS or GPS, the UE alsomaintains/manages the UE velocity. The UE adjusts the cell reselectionparameters in consideration of the mobility state.

If it is required to establish an RRC connection at a certain time atstep 910, the UE establishes an RRC connection in the current servingcell at step 915. Once the RRC connection setup has completed (or duringthe RRC connection setup procedure), the UE reports the followinginformation to the eNB at step 920:

-   -   Mobility state maintained and managed in idle state and related        information    -   Real velocity of UE (only when the UE velocity acquired with        assistance of GNSS is recorded)    -   GNSS operation-related information, e.g. current operation and        past operation history

The UE monitors to receive a mobility state report configuration messageat step 925 and, if the message is received, the UE monitors themobility state at step 930. The mobility state report configurationmessage includes the following information:

-   -   Mobility state determination criteria: velocity_high and        velocity_medium    -   Reference velocity for triggering mobility state report: if the        UE's velocity higher equal to or higher than the reference        velocity is maintained over a predetermined duration, the UE        reports mobility state.

If the velocity, which is measured with the assistance of GNSS, is equalto or higher than velocity_high and is maintained over a predeterminedduration, the UE determines that the mobility state 2 is high-mobilitystate. If the velocity lower than the velocity_high and equal to orhigher than velocity_medium is maintained over a predetermined duration,the UE determines that the mobility state 2 is medium-mobility state.

If the GNSS is activated, the UE determines current mobility state basedon the current velocity. If the mobility state report condition isfulfilled at step 935, the UE generates a mobility state report messageto report the new mobility state to the eNB at step 940. For example,the mobility state report condition may be fulfilled when the currentmobility state differs from the previous mobility state. Also, themobility state report condition may be fulfilled when the currentvelocity is higher than a predetermined reference velocity.

FIG. 10 is a block diagram illustrating a configuration of the UEaccording to an exemplary embodiment of the present invention.

Referring to FIG. 10, the UE includes a transceiver 1005, a controller1010, a multiplexer/demultiplexer 1020, higher layer processors 1025 and1030, and a control message processor 1035.

The transceiver 1005 receives data and control signals through adownlink channel of the serving cell and transmits data and controlsignal through an uplink channel. In the case that multiple servingcells are configured, the transceiver 1005 is capable of transmittingand receiving data con control signals through multiple serving cells.

The multiplexer/demultiplexer 1020 multiplexes the data generated by thehigher layer processors 1025 and 1030 and the control message processor1035 and demultiplexes the data received by the transceiver 1005 todeliver the demultiplexed data to appropriate processors, i.e. thehigher layer processors 1025 and 1030 and the control message processor1035.

The control message processor 1035 processes the control messagereceived form the eNB to takes an appropriate action. For example, ifDRX-related parameters are received, the control message processor 1035delivers these parameters to the controller 1010.

The higher layer processor 1025 or 1030 is configured per service toprocess the data generated by a user service such as File TransferProtocol (FTP) and Voice over Internet Protocol (VoIP) and transfer theprocessed data to the multiplexer/demultiplexer 1020, processes the datafrom the multiplexer/demultiplexer 1020, and delivers the processed datato the service application running on the higher layer.

The controller 1010 analyzes the scheduling command, e.g. uplink grant,received by the transceiver 1005 and controls the transceiver 1005 andthe multiplexer/demultiplexer 1020 to perform uplink transmission withappropriate transmission resource at appropriate timing. The controller1010 controls the random access procedure and the mobility statemanagement procedure. The controller 1010 may control the operationsassociated with the UE as described with reference to FIGS. 5, 6, 7, 8,and 9.

The controller 1010 controls the random access procedure in the primarycell (PCell). The controller 1010 detects the random access trigger in asecondary cell (SCell) and receives the information necessary forperforming random access to the SCell from the PCell. The controller1010 transmits a preamble to the SCell based on the received informationand controls the UE to monitor the primary cell to receive a RandomAccess Response for the SCell.

In this case, the information for use in the random access to the SCellmay include the maximum preamble transmission times or random accesstransmission resource information. The control unit 1010 controls the UEto monitor to receive the random access response for the SCell using therandom access response window size set for use in the PCell.

If no valid Random Access Response for the SCell is received in apredetermined time, the controller 1010 controls the UE to retransmitthe preamble in the SCell and, if a valid Random Access Response isreceived, controls the UE to transmit/receive data in the SCell based onthe information carried in the Random Access Response.

FIG. 11 is a block diagram illustrating a configuration of the eNBaccording to an exemplary embodiment of the present invention.

Referring to FIG. 11, the eNB according to an exemplary embodiment ofthe present invention includes a transceiver 1105, a controller 1110, amultiplexer/demultiplexer 1120, various higher layer processors 1125 and1130, a scheduler 1115, and a control message processor 1135.

The transceiver 1105 transmits data and control signals on a downlinkcarrier and receives data and control signals on an uplink carrier. Inthe case that multiple carriers are configured, the transceiver 1105transmits and receives the data and control signals on the multiplecarriers.

The multiplexer/demultiplexer 1120 multiplexes the data generated by thehigher layer processor 1125 and 1130 and the control message processor1135 and demultiplexes the data received by the transceiver 1105 todeliver the demultiplexed data to at least one of the higher layerprocessors 1125 and 1130 and the control message processor 1135 and thecontroller 1110. The control message processor 1135 processes themessage transmitted by the UE and takes a necessary action or generatesa control message to be transmitted to the UE to the higher layer.

The higher layer processor 1125 or 1130 is configured per bearer toprocess the data received from the S-GW or other eNB and generate RLCPDU to the multiplexer/demultiplexer 1120 and processes the RLC PDU fromthe multiplexer/demultiplexer 1120 and generates PDCP SDI to the S-GW orother eNB.

The scheduler 1115 allocates transmission resource to the UE at anappropriate time in consideration of the buffer status of the UE,channel status, and active time of the UE; and controls the transceiverto process the signals transmitted by the UE or to be transmitted to theUE.

The controller 1110 controls the random access procedure and mobilitystate management procedure. The controller 1110 controls the operationsassociated with the UE as described with reference to FIGS. 5, 6, 7, 8,and 9.

As described above, a data transmission method and apparatus accordingto exemplary embodiments of the present invention is advantageous inperforming random access in SCells by reusing a part of the informationconfigured for use in the PCell and furthermore in improving SCellrandom access efficiency through the PCell information reuse. Also, adata transmission method and apparatus according to exemplaryembodiments of the present invention is capable of improving SCelluplink performance and minimizing UE complexity.

While the invention has been shown and described with reference tocertain exemplary embodiments thereof, it will be understood by thoseskilled in the art that various changes in form and details may be madetherein without departing from the spirit and scope of the invention asdefined by the appended claims and their equivalents.

What is claimed is:
 1. A random access method of a terminal in a mobile communication system supporting carrier aggregation, the method comprising: transmitting, on a primary cell, a first random access preamble; receiving, on the primary cell, a first random access response message corresponding to the first random access preamble; transmitting, on the primary cell, a first physical uplink shared channel (PUSCH) according to a first uplink grant included in the first random access response message; transmitting, on a secondary cell, a second random access preamble; receiving, on the primary cell, a second random access response message corresponding to the second random access preamble; determining a transmission power for a second PUSCH based on a transmission power control (TPC) command included in the second random access response; and transmitting, on the secondary cell, the second PUSCH according to the determined transmission power and a second uplink grant included in the second random access response message.
 2. The method of claim 1, further comprising: receiving system information including information associated with the primary cell or the secondary cell.
 3. The method of claim 2, wherein the system information includes a duration of a random access response window and a maximum number of preamble transmissions.
 4. The method of claim 1, further comprising: receiving a higher layer message including a maximum number of preamble transmissions for the secondary cell and random access transmission resource information for the secondary cell.
 5. The method of claim 1, wherein the receiving of the second random access response message comprises: monitoring a control channel of the primary cell to receive the second random access response message identified by a random access radio network temporary identifier (RA-RNTI).
 6. The method of claim 1, wherein the receiving of the second random access response message comprises: monitoring a control channel of the primary cell to receive the second random access response message based on random access response window size information included in system information transmitted from the primary cell.
 7. The method of claim 1, wherein the receiving of the second random access response message comprises: determining that the second random access response message is received if the second random access response message includes a random access preamble identifier corresponding to the transmitted second random access preamble.
 8. The method of claim 1, wherein the second random access response message includes timing advance command information for the secondary cell.
 9. A terminal for performing a random access in a mobile communication system supporting carrier aggregation, the terminal comprising: a transceiver configured to transmit and receive a signal; and a controller configured to: transmit, on a primary cell, a first random access preamble, receive, on the primary cell, a first random access response message corresponding to the first random access preamble, transmit, on the primary cell, a first physical uplink shared channel (PUSCH) according to a first uplink grant included in the first random access response message, transmit, on a secondary cell, a second random access preamble, receive, on a primary cell, a second random access response message corresponding to the second random access preamble, determine a transmission power for a second PUSCH based on a transmission power control (TPC) command included in the second random access response, and transmit, on the secondary cell, the second PUSCH according to the determined transmission power and a second uplink grant included in the second random access response message.
 10. The terminal of claim 9, wherein the controller is further configured to receive system information including information associated with the primary cell or the secondary cell.
 11. The terminal of claim 10, wherein the system information includes a duration of a random access response window and a maximum number of preamble transmissions.
 12. The terminal of claim 9, wherein the controller is further configured to receive a higher layer message including a maximum number of preamble transmissions for the secondary cell and random access transmission resource information for the secondary cell.
 13. The terminal of claim 9, wherein the controller is further configured to monitor a control channel of the primary cell to receive the second random access response message identified by a random access radio network temporary identifier (RA-RNTI).
 14. The terminal of claim 9, wherein the controller is further configured to monitor a control channel of the primary cell to receive the second random access response message based on random access response window size information included in system information transmitted from the primary cell.
 15. The terminal of claim 9, wherein the controller is further configured to determine that the second random access response message is received if the second random access response message includes a random access preamble identifier corresponding to the transmitted second random access preamble.
 16. The terminal of claim 9, wherein the second random access response message includes timing advance command information for the secondary cell.
 17. A base station for supporting a random access in a mobile communication system supporting carrier aggregation, the base station comprising: a transceiver configured to transmit and receive a signal; and a controller configured to: receive, on a primary cell, a first random access preamble; transmit, on the primary cell, a first random access response message corresponding to the first random access preamble; receive, on the primary cell, a first physical uplink shared channel (PUSCH) according to a first uplink grant included in the first random access response message; receive, on a secondary cell, a second random access preamble from a terminal, transmit, on a primary cell, a second random access response message, including a transmission power control (TPC) command, corresponding to the second random access preamble to the terminal, and receive, on the secondary cell, a second PUSCH according to a transmission power of the terminal determined based on the TPC command and a second uplink grant included in the second random access response message.
 18. The base station of claim 17, wherein the controller is further configured to transmit system information including information associated with the primary cell or the secondary cell.
 19. The base station of claim 18, wherein the system information includes a duration of a random access response window, and a maximum number of preamble transmissions.
 20. The base station of claim 17, wherein the controller is further configured to transmit a higher layer message including a maximum number of preamble transmissions for the secondary cell and random access transmission resource information for the secondary cell, wherein a control channel of the primary cell is monitored by the terminal to receive the second random access response message identified by a random access radio network temporary identifier (RA-RNTI), wherein a control channel of the primary cell is monitored by the terminal to receive the second random access response message based on random access response window size information included in system information transmitted from the primary cell, wherein the terminal determines that the second random access response message is received if the second random access response message includes a random access preamble identifier corresponding to the transmitted second random access preamble, and wherein the second random access response message includes timing advance command information for the secondary cell. 